Organic thin film electroluminescent device

Abstract

A cathode is formed of an alloy, which includes 0.01 to 5 mol % of scandium and 0.01 to 0.3 mol % of alkali metal. Base of the alloy has a work function greater than or equal to 4 eV and is silver, aluminum, or indium or the alloy thereof. Thickness of the cathode is preferably 1 to 30 nm. Also, as a cathode protection layer, an aluminum alloy is formed on the cathode in a thickness greater than or equal to 50 nm, the aluminum alloy containing 0.1 to 5 mol % of silicon, copper, scandium and/or manganese.

What is claimed is: 
     
       1. An organic thin film electroluminescent diode comprising: an anode;   a cathode including a metal or alloy, the metal or alloy having a work function greater than or equal to 4 eV, the cathode further including 0.01 to 5 mol % of scandium and 0.01 to 0.3 mol % of alkali metal; and   an organic thin film layer disposed between said anode and cathode and having at least one light emitting layer.   
     
     
       2. An organic thin film electroluminescent diode as set forth in claim 1, wherein the thickness of said cathode is in a range of 1 to 30 nm, and said organic thin film electroluminescent diode includes a cathode protection layer in a thickness of 50 to 3000 nm formed on said cathode. 
     
     
       3. An organic thin film electroluminescent diode as set forth in claim 2, wherein said cathode protection layer is formed of an aluminum alloy containing at least one element selected from a group consisting of scandium, silicon, manganese, and copper, in a content of 0.1 to 5 mol %. 
     
     
       4. An organic thin film electroluminescent diode as set forth in claim 1, wherein a work function of said cathode is less than 4 eV, due to the scandium and the alkali metal being included in said cathode. 
     
     
       5. An organic thin film electroluminescent diode as set forth in claim 4, wherein the metal or alloy having the work function of greater than or equal to 4 eV is aluminum. 
     
     
       6. An organic thin film electroluminescent diode as set forth in claim 1, wherein the organic thin film electroluminescent diode includes a cathode protection layer in a thickness of 50 to 3000 nm formed on said cathode. 
     
     
       7. An organic thin film electroluminescent diode, comprising: an anode;   a cathode formed of a metal or alloy containing 0.01 to 5 mol % of scandium and 0.01 to 0.3 mol % of alkali metal; and   an organic thin film layer disposed between said anode and cathode and having at least one light emitting layer,   wherein said cathode is formed of a material selected from a group consisting of silver, aluminum, indium, and an alloy thereof, the material containing said scandium and alkali metal.